The present invention relates to a glass bottle sealing of the mouth by high-frequency heat sealing.
Glass bottles for high-frequency heat sealing have hitherto been known wherein a sealing material (a film formed of a synthetic resin laminated to aluminum foil at the undersurface) is placed on the mouth of a glass bottle and undergoes high-frequency heating in capping condition, and the film formed of a synthetic resin of a sealing material is welded to an apical part of the mouth to seal. The apical parts of the mouths of conventional glass bottles are smooth.
In the glass bottles sealed by high-frequency heating, the presence of portions low in sealing strength is liable to break the seal. Since the breaking of the seal must be absolutely avoided, the sealing strength must be increased as a whole by making high frequency act strongly. Then areas having extremely high sealing strength are produced, and there arises a problem of making difficult the breaking of the sealing material. The invention has been carried out, in the glass bottles of this kind, aiming at depressing the dispersion of sealing strength as lowly as possible to improve the ease of both sealing and unsealing.
The invention is a glass bottle for high-frequency heat sealing characterized by forming a rough surface having minute unevenness in the proximity of the apical part of the mouth contacting a sealing material.
Formation of the rough surface having minute unevenness in the proximity of the apical part of the mouth produces the following phenomena:
(1) A contact area between the sealing material and the glass surface decreases, and the quantity of heat taken by the glass from the sealing material decreases.
(2) A bond area increases.
(3) An anchor effect is generated.
Thus the sealing strength increases, and simultaneously the dispersion of the sealing strength decreases. This needs no excessive increase in the sealing strength by making high-frequency act strong to facilitate the breaking of the sealing material.